Millennial, which is the largest remaining independent ad network (AdMob was bought by Google and Apple acquired Quattro), has had a banner year as the mobile advertising market explodes. In terms of mobile advertising marketshare, the IDC estimates Millennial follows in a close third to both Google and Apple. Millennialâ€™s ads reach 63 million of a total of 77 million mobile web users in the U.S., or 81 percent of the U.S. mobile web.

Co-founded by ad exec Paul Palmieri, Millennial Media has flown relatively under the radar for how prominent the company is in the mobile ad space. And the company has avoided some of the drama that took place between AdMob and Apple last year.

While Millennial has a fairly thriving independent ad network, the company also operates and manages private mobile ad networks for large media companies and conglomerates that have multiple apps and sites, essentially powering a self-service ad network for these companies. Millennial also has a deal with a â€œprominent internet media companyâ€ (but declines to name the company) that has completely outsourced its mobile advertising to Millennial.

Palmieri says that while competing with the likes of Google and Apple is challenging, the company’s focus on bringing advertising cross-platform to a variety of mobile devices has helped the network compete (as opposed to Apple which is focused on the iOS platform).

And all of this business has helped the company grow its top line. Millennial tripled revenue in 2010 from 2009 and achieved profitability. According to IDC research published last December, Millennial Media was on target to make $35 million in U.S. mobile advertising revenue for 2009, so revenues could be well over $100 million. Last year the company acquired analytics startup TapMetrics and plans to “acquire aggressively this year.”

And Palmieri has expressed his commitment to remaining independent and has ambitions to take the company public, possibly becoming the largest publicly traded independent advertising network in the space.

He adds that Millennial didn’t need to raise funding at this time but saw the opportunity to use the money to grow aggressively (particularly in international markets like Asia and Europe). “In the end, this is more about how we are going to win,” he says.